Pocket sized adjustable knife sharpener

ABSTRACT

A knife blade sharpener including two generally circular sharpening members pivotally mounted about a pivot axis and having opposed grinding edges. The grinding edges are located along one side of a notch formed in each of the generally circular sharpening members and can be brought to face one another, adjustably subtending an obtuse angle therebetween. The pivot axis may be established by a screw and a knurled nut enabling the user to tighten the two generally circular sharpening members together at a selected subtended angle for sharpening. A knife blade may be drawn through a wedge shaped gap between the two mutually facing grinding edges, and thereby sharpened. The knife blade sharpener has resilient gripping pads and a holster which facilitates gripping as well as for stowage.

FIELD OF THE INVENTION

The present invention relates to sharpening tools, and more particularly, to a hand held knife sharpener.

BACKGROUND OF THE INVENTION

Knives will become dulled with use and therefore periodically require sharpening. It is possible to maintain a grindstone for this purpose. However, a single grindstone can result in uneven grinding along the length of the knife blade edge. Also, a grindstone may be cumbersome to carry and use if large, and may be easily lost if small.

SUMMARY OF THE INVENTION

The present invention addresses the above stated need by providing a compact knife blade sharpener having opposed grinding edges. The grinding edges are each formed on a generally circular sharpening member both mounted about a pivot axis for mutual pivot or rotation about the pivot axis. The generally circular sharpening members are pivotally adjusted such that a wedge shaped gap separating the opposed grinding edges corresponds to a cross sectional profile of a knife blade being sharpened. The two generally circular sharpening members are locked in the selected adjustment. The knife blade is drawn through the gap and contacted with both of the grinding edges.

The knife blade sharpener may have resilient pads on the generally circular sharpening members to facilitate grip while sharpening. A holster may be provided to further facilitate grip and also for storage.

It is an object of the invention to provide improved elements and arrangements thereof by apparatus for the purposes described which is inexpensive, dependable, and fully effective in accomplishing its intended purposes.

These and other objects of the present invention will become readily apparent upon further review of the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Various objects, features, and attendant advantages of the present invention will become more fully appreciated as the same becomes better understood when considered in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the several views, and wherein:

FIG. 1 is a perspective view of a knife blade sharpener, according to at least one aspect of the invention;

FIG. 2 is a diagrammatic plan view of a major component of a knife blade sharpener, according to at least one aspect of the invention;

FIG. 3 is an exploded side view of a knife blade sharpener, according to at least one aspect of the invention;

FIG. 4 is a perspective view of a knife blade sharpener, according to at least one aspect of the invention;

FIG. 5 is an environmental plan view of a knife blade sharpener, according to at least one aspect of the invention, with a knife blade shown in cross section;

FIG. 6 is a plan view of a knife blade sharpener and a holster therefor, according to at least one aspect of the invention;

FIG. 7 is a plan view of a knife blade sharpener explaining a geometric feature of a grinding edge; and

FIG. 8 is a block diagram summarizing steps of a method of sharpening a knife, according to at least one aspect of the invention

DETAILED DESCRIPTION

Referring first to FIG. 1, according to at least one aspect of the invention, a knife blade sharpener 100 includes a first sharpening member 102 having a first grinding edge 104 and a second sharpening member 106 having a second grinding edge 108. Referring also to FIG. 2, which generically and diagrammatically illustrates overall configuration of each of the first and second sharpening members 102, 106, the first and second sharpening members 102, 106 each have a generally circular circumferential surface 105A or 105B with a wedge shaped notch 112. In FIG. 2, the wedge shaped notch 112 is indicated by an arrow 110 indicating magnitude of an angle subtended by the sides 114, 116 of the notch 112. The notch 112 may subtend an angle of about ninety degrees of the generally circular circumferential surface 105 which generically represents the generally circular circumferential surfaces 105A and 105B. The notches of the first and second sharpening members 102, 106 represented by the wedge shaped notch 112 in FIG. 2 may be equal in subtended angular magnitude.

The first grinding edge 104 of the first sharpening member 102 is along one side of the notch (such as the notch represented as 112 in FIG. 2). Similarly, the second grinding 108 edge of the second sharpening member 106 is along one side of the notch, such that the first and grinding edges 104, 108 face one another after the first and second generally circular sharpening members are locked together by the screw 118 and nut 120.

The first and second grinding edges 104, 108 may be part of a strip formed from a carbide material, such as for example silicon carbide or tungsten carbide. Each strip may be adhered to its associated first or second generally circular sharpening member 102 or 106, which may be formed from a metal such as aluminum or steel, or alloys thereof.

Also referring to FIGS. 3 and 4, the first and second sharpening members 102, 106 are pivotally secured to a pivot member. An illustrative pivot member may comprise a screw 118 and a threadably compatible nut 120 having an enlarged head bearing a knurled surface 122. The pivot member establishes a pivot axis 124. The first and second sharpening members 102, 106 are pivotally secured to the pivot member to pivot about the pivot axis 124 such that the first grinding edge 104 and the second grinding edge 108 have a common point of intersection 126 (FIG. 4), and are infinitely angularly adjustable such that the first and second grinding edges 104, 108 subtend an angle (e.g., the angle 128 in FIG. 4) of variable angular magnitude. The angle (e.g., the angle 128) is of variable angular magnitude in that it is adjustable. Once set to a selected magnitude, which preferably corresponds to the angle of a profile of a knife blade 10 (as seen in FIG. 5, the first and second sharpening members 102, 106 are locked together such that the angle is set until the next adjustment. Obviously, only that portion of the knife blade 10 near the point is of the critical angle to which the knife blade sharpener 100 is set.

The pivot member and a lock locking the first and second sharpening members 102, 106 together may be unitary, thereby serving both to establish the pivot axis 124 and also as a lock which is configured to releasably secure the first and second grinding edges 104, 108 at a selected subtended angular relation to accommodate the knife blade 10.

The subtended angular relation may be set if the angle of the critical part of the knife blade 10 is known. If not known, this angle may be measured. Once the angle of the knife blade 10 is known, the knife blade sharpener 100 may be adjusted by using an indicating feature. One of the first and second sharpening members 102, 106 (or, if desired, both) includes indicia 130 indicative of the angle (e.g., the angle 128) subtended by the first and second grinding edges 104, 108. The notch (corresponding to the notch 112 seen in FIG. 2) of the first sharpening member 102 or the second sharpening member 106 includes a first side (such as the first side 114 in FIG. 2) including the grinding edge 104 or 108 and a second side (such as the side 116 in FIG. 2), the second side having a beveled portion 132 (FIGS. 1 and 4) resulting in an edge 134 immediately proximate the indicia 130. Because each of the first and second sharpening members 102, 106 has more than nominal thickness, errors of parallax could interfere with accurate setting of the angle (e.g., the angle 128). The beveled portion 132 causes the edge 134 to be so close to the indicia 130 that errors of parallax will not occur.

If the cutting angle of the knife (e.g., the knife 12 in FIG. 5) is not known, it may be measured by applying a coloring agent such as magic marker to the knife blade near the cutting edge, and drawing it through the knife blade sharpener 100. When the first and second grinding edges 104, 108 are spaced apart such that a slight removal of the coloring agent occurs on each side of the blade of the knife, the knife blade sharpener 100 is adjusted to the cutting angle of the knife. At this point, the indicia 130 indicates the cutting angle, and the indicia may be read, and the value remembered or recorded.

Best seen in FIGS. 1 and 4, the knife blade sharpener 100 may include at least one and if desired, two gripping pads 136, 138 on one or both of the first and second sharpening members 102, 106. The gripping pad 136 or 138 may be fabricated from a synthetic substance such as neoprene.

Turning now to FIG. 6, the knife blade sharpener 100 may include a separate holster 140 configured to receive the knife blade sharpener 100 in close cooperation therein. The holster 140 forms a pocket having a first side 142 and an opposed second slide 144, each side 142 or 144 including a slot 146 configured to avoid contact with the pivot member when the knife blade sharpener 100 is slid into the pocket. An arrow 148 indicates the direction of insertion of the knife blade sharpener 100 into the holster 140 and withdrawal from the holster 140. The holster 140 not only protects the knife blade sharpener 100 from damage as well as protecting people from potential injurious contact with the grinding edges 104, 108, but also facilitates grip of the knife blade sharpener 100 when being used. Grip may be by hand, or alternatively, within a holder such as a vise (not shown). The holster 140 may be fabricated from leather, among other materials.

FIG. 7 shows a geometric characteristic of the knife blade sharpener 100, wherein the first grinding edge 104 of the first sharpening member 102 is offset from a radius 150 radiating from the pivot axis 124. The first grinding edge 104 is displaced or projects into the notch (such as the notch 112 of FIG. 2. The first grinding edge 104 aligns with a projection line 152 which is displaced to the right of the radius 150 in FIG. 7, by a distance of about three thirty-seconds of an inch, with the overall diameter 154 of the first sharpening member 102 being about two and seven-eighths inches. Alternatively stated, the degree of offset of the first grinding edge 104 is about one thirtieth of the overall diameter 154 of the first sharpening member 102. The first grinding edge 104 is parallel to the radius 150.

The second sharpening member 106 (see FIG. 4) may have the same characteristics relating to offset as the first sharpening member 102.

As a method of sharpening a knife blade (e.g., the knife blade 12) as shown in FIG. 8, the method includes providing two generally circular sharpening members (e.g., the generally circular sharpening members 102, 106) pivotally mounted about a pivot axis (e.g., the pivot axis 124) and having opposed grinding edges (e.g., the grinding edges 104, 108), the grinding edges each located along one side of a notch (e.g., the notch 112 in FIG. 5) formed in each of the generally circular sharpening members (step 160). The method includes adjusting the two generally circular sharpening members to a selected subtended angular relationship between the two generally circular sharpening members such that a wedge shaped gap (e.g., the gap 128 in FIG. 4) exists between the opposed grinding edges, the selected subtended angular relationship corresponding to an angular configuration of the knife blade (step 162). The method includes securing the two generally circular sharpening members in the adjusted subtended angular relationship (step 164), and drawing the knife blade through a gap between the two grinding edges in contact with the two grinding edges (as seen for example in FIG. 5) (step 166).

While the present invention has been described in connection with what is considered the most practical and preferred embodiment, it is to be understood that the present invention is not to be limited to the disclosed arrangements, but is intended to cover various arrangements which are included within the spirit and scope of the broadest possible interpretation of the appended claims so as to encompass all modifications and equivalent arrangements which are possible. 

I claim:
 1. A knife blade sharpener, comprising: a first sharpening member having a first grinding edge and a second sharpening member having a second grinding edge; a pivot member establishing a pivot axis, the first sharpening member and the second sharpening member pivotally secured to the pivot member to pivot about the pivot axis such that the first grinding edge and the second grinding edge have a common point of intersection and are infinitely angularly adjustable such that the first grinding edge and the second grinding edge subtend an angle of variable angular magnitude; and a lock configured to releasably secure the first grinding edge and the second grinding edge at a selected subtended angular relation.
 2. The knife blade sharpener of claim 1, wherein the first sharpening member and the second sharpening member each have a generally circular circumferential surface with a wedge shaped notch.
 3. The knife blade sharpener of claim 2, wherein the first grinding edge of the first sharpening member is offset from a radius radiating from the pivot axis, is parallel to the radius, and projects into the notch.
 4. The knife blade sharpener of claim 3, wherein the degree of offset of the first grinding edge is about one thirtieth of the overall diameter of the first sharpening member.
 5. The knife blade sharpener of claim 3, wherein the degree of offset of the first grinding edge is about one thirtieth of the overall diameter of the first sharpening member, and the second grinding edge of the second sharpening member is offset from a radius radiating from the pivot axis, and projects into the notch, and the degree of offset of the second grinding edge is about one thirtieth of the overall diameter of the second sharpening member.
 6. The knife blade sharpener of claim 2, wherein the wedge shaped notch subtends an angle of about ninety degrees of the generally circular circumferential surface.
 7. The knife blade sharpener of claim 2, wherein the notch of first sharpening member and the notch of the second sharpening member are equal in subtended angular magnitude.
 8. The knife blade sharpener of claim 2, wherein the first grinding edge of the first sharpening member is along one side of the notch, and the second grinding edge of the second sharpening member is along the opposed side of the notch.
 9. The knife blade sharpener of claim 1, wherein the pivot member and the lock are unitary with one another.
 10. The knife blade sharpener of claim 1, wherein the pivot member comprises a screw and a knurled nut.
 11. The knife blade sharpener of claim 1, wherein at least one of the first sharpening member and the second sharpening member comprises indicia indicative of an angle subtended by the first grinding edge and the second grinding edge.
 12. The knife blade sharpener of claim 1, wherein one of the first sharpening member and the second sharpening member comprises indicia indicative of an angle subtended by the first grinding edge and the second grinding edge.
 13. The knife blade sharpener of claim 12, wherein the notch of the first sharpening member or the second sharpening member comprising the indicia includes a first side including the grinding edge and an opposed second side, the second side having a beveled portion resulting in an edge immediately proximate the indicia.
 14. The knife blade sharpener of claim 1, further comprising at least one gripping pad on at least one of the first sharpening member and the second sharpening member.
 15. The knife blade sharpener of claim 14, wherein the gripping pad is fabricated from a synthetic substance.
 16. The knife blade sharpener of claim 1, further comprising a first gripping pad on the first sharpening member and a second gripping pad on the second sharpening member.
 17. The knife blade sharpener of claim 1, further including a separate holster configured to receive the knife blade sharpener in close cooperation therein.
 18. The knife blade sharpener of claim 17, wherein the holster comprises a pocket having a first side and an opposed second slide, wherein the first side and the second side each includes a slot configured to avoid contact with the pivot member when the knife blade sharpener is slid into the pocket.
 19. The knife blade sharpener of claim 1, wherein each of the grinding edges is formed from a carbide material.
 20. A method of sharpening a knife blade, comprising: providing two generally circular sharpening members pivotally mounted about a pivot axis and having opposed grinding edges, the grinding edges each located along one side of a notch formed in each of the generally circular sharpening members; adjusting the two generally circular sharpening members to a selected subtended angular relationship between the two generally circular sharpening members such that a wedge shaped gap exists between the opposed grinding edges, the selected subtended angular relationship corresponding to an angular configuration of the knife blade; securing the two generally circular sharpening members in the adjusted subtended angular relationship; and drawing the knife blade through a gap between the two grinding edges in contact with at least one of the two grinding edges. 